Limpets

There are two separate species of shellfish which are referred to as limpets in UK sea angling: the common limpet (Patella vulgata) and the slipper limpet (Crepidula fornicata). This causes much confusion amongst sea anglers. When the term ‘limpet’ is used anglers in the north of England and Scotland are likely to think of the common limpet, while anglers in the south are more than likely to believe the slipper limpet is being referred to.

Update

While slipper limpets were a relatively popular bait around parts of the UK where they are present they are actually an invasive species which is not native to the British Isles. They smother native UK species and also out-compete native species for food, leading to serious damage to the shellfish beds of valuable commercial species such as scallops and oysters. For these reasons in Spring 2015 the UK government made it an offence to release live or fresh slipper limpets into the sea, as this may spread the eggs and larvae into areas of the UK where the species is not yet present, such as the coast of northern England and Scotland. This also includes using slipper limpets in angling, meaning that it is now an offence to use slipper limpets as a sea fishing bait. This article was written and published in late 2012 when it was perfectly legal to use slipper limpets as a sea fishing bait, and the information is left on this page for reference purposes only. Read the official government press release on this issue by clicking here.

Left, a cone-shaped common limpet attached to a rock face and right, an empty shell of a slipper limpet, which are often found stacked together.

Common Limpet

The common limpet (Patella vulgata) – also known as the European limpet – is an edible (although not widely eaten) species of ‘true’ limpet which is abundant across the whole of the British Isles, and indeed most of Europe.

Description and Life Cycle

The underside of a common limpet with the foot visible.

The common limpet is made up of an extremely strong cone shaped shell and a soft fleshy body inside. The whole bottom section of their body consists of a large ‘foot’ which they use to secure themselves to rocks. The shell is usually a light grey to white in colour, and the flesh inside is usually a light orange. Limpets live by attaching themselves to rock surfaces with their powerful foot which makes up the whole of the bottom section of their body. Common limpets are found anywhere in the inter-tidal zone or in shallow water and can live happily in water down to ten metres deep or so.

A home scar left by a very large common limpet.

When the tide is out and limpets are exposed they clamp down onto the rock in order to prevent drying out and to protect themselves from predators. However, when the tide is in then limpets feed by very slowly moving across rocks and eating the algae and microscopic marine lifeforms they come across. Common limpets make an indentation in the rock (called a home scar) on which they live and although they move around to feed they always return to the same indentation. When threatened limpets can clamp themselves to the rock surface with great force, making them practically invulnerable to predators. Indeed, according to researchers at the University of Portsmouth, the tiny ‘teeth’ than common limpets use to attach themselves to rocks may well be the strongest natural material in the world. The common limpet breeds by the males releasing sperm into the sea where it is collected by the female and used to fertilise eggs. Immature limpets are free-swimming plankton for the first period of their life before attaching themselves to rocks and beginning their life as a shellfish. Common limpets can be 5cm across at their very largest, but most are around half of this size. It is thought that in the right conditions the common limpet can live for up to twenty years.

Gathering Common Limpets

Common limpets are easy to find and most rocky areas will have a population of common limpets which can be accessed at low tide.

Common limpets are easy to find attached to large rocks and cliff faces which become exposed as the tide ebbs. To collect them put a blade between the shell and the rock and quickly ease them from the rock surface. Do not tap or nudge them first as this will see them clamp down and once they have done this they will prove near-impossible to remove and it will be better to move onto a new unclamped limpet, rather than persist on trying to remove a clamped one. The flesh of limpets can be scooped out of the shell as needed with a blunt mussel knife or spoon. As with all shellfish collecting be careful about how many are taken as whole areas can be depleted of species by over-enthusiastic bait collectors. This leads to much more serious knock-on effects with the whole marine ecosystem of an area, as limpets plan an important role in keeping algae levels under control. Anglers should only take what is needed and ensure that all smaller limpets and a lot of larger breeding age ones are left after a collecting session. A better idea is to spread collecting over a number of areas and a long period of time so one place does not become completely de-populated of this species. Shelled limpets can be frozen for future use, and made tougher by salting them prior to freezing.

Common Limpets Use as Bait and Bait Presentation

Like cockles and winkles, limpets do not make the best bait when presented on the seabed as they do not release a great deal of scent. In addition to this they are so well protected in their shells few fish will be used to feeding on them. Even a storm will not dislodge the common limpet from the sides of rocks, meaning that there are no conditions which will see this type of limpet being widely eaten by UK fish species. The only fish which eats the common limpet is the wrasse, as they have the powerful jaws needed to wrench limpets off rocks and consume the flesh inside. It is certainly worth putting a few limpets onto a size 1 hook and float fishing it down the side of a harbour wall or rock face and waiting for the wrasse to bite.

However, anglers do still have a use for the common limpet. They can be used to bulk up other baits in a cocktail such as ragworm, lugworm, peeler crab or mackerel. Another use is as a tipping bait. Since the flesh of the common limpet is very tough a full small limpet, or half a bigger one can be pushed over the hookpoint of a soft bait such as peeler crab or razorfish to help prevent the soft bait coming off the hook during the cast or when hitting the water. As stated common limpets can be salted prior to going fishing in order to toughen them up further and make them even better at keeping other baits on the hook.

Slipper Limpet

The slipper limpet (Crepidula fornicata) is a different species altogether and is technically a sea snail rather than a true limpet. They are known by a wide range of other names such as slipper shell, boat shell, slipper snail and Atlantic slipper, but it is the slipper limpet name which seems to have stuck in the United Kingdom.

As the update section above states slipper limpets are an invasive species and it is now an offence to use them as a sea fishing bait in the UK. All of the information below is shown for reference purposes only.

Description and Life Cycle

Slipper limpets consist of a soft creature inside a hard shell. This shell looks like the hull of a boat or a slipper on one side, and on the other it is half covered with a white section known as the ‘deck.’ Slipper limpets do not move around to look for food but instead stay in the same place and filter-feed by straining microscopic food and plankton through their bodies. A fully grown slipper limpet can be around 6cm long but most are smaller than this.

They are not a native species to Britain and actually originate from the coasts of North and South America. They are thought to have been brought to Britain in consignments of oysters and mussels in the first half of the twentieth century and are now present throughout much of the south-east and southern coasts, as well as the southern parts of Wales. They have also been reported in parts of the Republic of Ireland. It is thought that the colder waters of northern England and Scotland prevent this species from spreading further, although warming seas mean that they may be able to spread all around the UK in the near future. They are classed as an invasive species by both the British and Irish authorities as they can smother oyster beds and out-compete other native shellfish species such as scallops for food. They have also become present in seas as far away as Japan and Australia. Slipper limpets are not eaten by humans and have no commercial value.

A chain of slipper limpets.

Slipper limpets are often found together in chains or stacks. This is because of the unusual way in which they reproduce. The slipper limpet cannot breed by releasing sperm into the sea like a common limpet can. Instead they must be right next to each other and actually mate. This means that a male slipper limpet will attach himself to the shell of a female for his entire life and is in the correct place to breed. However, slipper limpets forming into stacks of ten are not uncommon and in exceptional circumstances there may be thirty or more. Only the bottom one will be female and the rest will be males. However, if the bottom slipper limpet dies the next one up will continue to cling to the empty shell and will transform into a female, ready to breed with the next limpet up. This will continue if the bottom slipper limpet again dies, so that the bottom live limpet in the chain is always female. Larvae will spread out and swim away from their birthplace, starting new chains elsewhere and quickly spreading slipper limpets along a coastline. Although they do not damage oysters directly the sheer number of sipper limpets means that oysters are out-competed for food and begin to reduce in number. Some areas which used to be abundant with oysters have become completely barren of this species due to the overwhelming number of slipper limpets which have become present.

The Use of Slipper Limpets as Bait

When sllipper limpets were used as a bait anglers could collect them by looking around rock pools and throughout the inter-tidal zone. However, the most effective way of collecting them was after a storm or period of bad weather when slipper limpets would have dislodged from rocks and could simply be collected from the beach. Slipper limpets could be taken from their shell by scooping them out with a blunt mussel knife. Many anglers sprinkled them with a little salt to toughen them up prior to using them as bait. They could also be frozen for future usage and some tackle shops and online bait dealers would offer them pre-shelled in frozen form. There was a school of thought that slipper limpets are a better bait when left for a day or two to go off before being frozen or used as bait, due to the increased scent and smell the slipper limpets will then contain.

A chain of slipper limpets dislodged from the rocks and onto a beach.

While slipper limpets were best collected after a storm this was also the time that they were best used as bait and could account for species such as cod, whiting, pouting, flounder, dab, Dover sole bass. However, as using slipper limpets as bait is now an offence, anglers should switch their attention to using a different type of bait.